This list will be updated as I find more classes that fit Jam. I'm also repeating some of the stuff from the Races page since they're racial classes.
WHAT CAN I PLAY IN JAMMER HEARTS.
Again, hypothetically anything, but here's some that I think fit particularly well:
MAGITEK ENGINEER -- The art of magitek originated with the mysterious Gnomes, who live on great hiveships out in the Lanes Between (e.g., space). They first brought this skill to the people of the kingdom of Radiant Garden centuries ago, whereupon the Gardens became the second greatest power in the galaxy, next to the Eared Empire. Some Imperial citizens have taken up the art, but the vast majority of Magitek Engineers are Human or Gnomish. Magitek Engineers make good livings as ship's mechanics.
MUSCLE WIZARD -- There's actually two flavors of Muscle Wizard -- Dark Knights, who were the secret police of the Kingdom of Radiant Garden, tended to wear a lot of black and are generally brooding fellows who manage their spells and the bonus hitpoints they get from them like the ebbing and flowing of their very souls, man. Dark Knights ALWAYS use knives to channel their spells.
Meanwhile, also in Radiant Garden, there was a pretty swag arcade with some fighting games like Street Fighter and also a magic 3D printing laser that could print anything (or digitize anything), and during the Fall some shit went wrong and now there's random fighting game characters wandering around Traverse.
BLUE MAGES -- Blue Magic is the pinnacle of Radiant magic, one of the truly unique spellcasting schools to come from that fallen place. Blue Mages are tougher, hardier wizards who learn their spells by being hit in the face by them, thus allowing them to learn enemy special abilities.
Other Final Fantasy Classes -- LAAAAAAAAATer
These are better detailed on the Races page, but I'll list 'em here too since THEY ARE ALSO CLASSES
Diving Belle (mermaid/merman)
Ghoulies (COMING SOON as I can transcribe Scrap's post)